The anti-oxidant potential of diphenyl diselenide and ebselen against low pH-mediated peroxidation processes in rat's liver preparation are unknown. For this purpose, we have determined anti-oxidant activities of both compounds at a range of various pH (7.4-5.4) values. Low pH increased the rate of lipid peroxidation in the absence of Fe(+2) (20 micromol) in liver homogenates. This higher extent of lipid peroxidation can be explained by the mobilized iron, which may come from reserves where it is weakly bound. The addition of iron (Fe) chelator desferoxamine (DFO, 1 mmol) to reaction medium completely inhibited the peroxidation processes at all studied pH values. Diphenyl diselenide (0-100 micromol) significantly protected lipid peroxidation at all studied pH values, while ebselen (0-100 micromol) did not offer any protection. The differences in activities of diphenyl diselenide and ebselen have been explained with reference to the active selenol formation using their catalytic reactions. The anti-oxidant potential of diphenyl diselenide is confirmed against acidosis-catalyzed oxidative stress in rat liver homogenates.